Defence chiefs visited an air base being upgraded by the American military in the Philippines amid territorial threats from China.

Defence Secretary Gilbert Teodoro and top army officials arrived on a Philippine Air Force (PAF) C-295 plane to inspect the Lumbia Air Base in Cagayan de Oro province in the Mindanao region on November 30.

Teodoro said the air base, which was being developed under the Philippines' Enhanced Defense Cooperation Agreement (EDCA) with the US, will improve humanitarian assistance and disaster response (HADR) in the typhoon-prone country.

He said: 'We will expedite the development because this will become the maintenance and training base of the 15th Strike Wing. This is where their assets will be housed.'

An air traffic control tower and a HADR warehouse capable of accommodating US reserve forces were under construction. The military hub is expected to be completed in 2026.

The Lumbia Air Base is one of nine EDCA sites in the Philippines funded by the US.

The agreement was signed in 2014 and will allow the US to send troops into the Philippines for extended stays. The pact will also let US forces build and operate in the joint EDCA bases.

Teodoro's visit came as three Chinese research vessels were spotted off the coasts of Luzon and Mindanao islands in November.

Expansionist China currently lays claim over almost the entire South China Sea, one of the world's busiest sea lanes. But a United Nations-backed tribunal in 2016 deemed its claims groundless.

The Communist rogue state - accused of genocide for its crimes against the Uyghur population - has been steadily increasing its influence in recent years through investment in developing countries.